1. Field of the Invention
The present invention relates to a catalytic gas phase (vapor phase) fluorination of 1,1,2-trichloroethane (140 or TCE) and/or 1,2-dichloroethene (1130 or DCE) using hydrogen fluoride (HF) to produce 1-chloro-2,2-difluoroethane (i.e. 1,1-difluoro-2-chloroethane or 142), as well as to the catalysts used in said gas phase fluorination.
2. Description of Related Art
1-Chloro-2,2-difluoroethane is known to be useful as a foam blowing agent and can be employed as a starting material in the preparation of agrochemicals or pharmaceuticals (cf. PCT/EP2011/059691). Several methods for the preparation of hydrocarbon fluorides in the gas phase are known (cf. WO 01/74483 and the prior art mentioned therein).
FR 2 783 820 A1 describes, for example, a method for the preparation of 142. In this preparation method 1,1,1-trichloroethane (T112) is fluorinated with HF in the gas or liquid phase. The gas phase reaction is conducted at a temperature between 120° C. and 400° C. using a solid chrome catalyst or a chrome catalyst deposited on carbon, Al2O3, or AlF3, or deposited on an oxyfluorinated aluminum support. The reaction of T112 with HF to T142 in the gas phase gave 78% of T142 at a conversion rate of T112 of 100%. The catalyst used for this reaction is said to consist of 58.6% fluorine, 25.9% aluminum, 6.4% nickel, 6.0% chrome and 3.1% oxygen. The density parameter of said catalyst is given to be 0.85 g/mL and the BET surface was 23 m2/g.
EP 1 008 575 A1 (which is an equivalent of US 2002/0183569 A1 and U.S. Pat. No. 6,063,969 B) describes a catalytic gas phase fluorination of 140 with HF for preparing 142. The catalyst can be supported or unsupported. It is preferred to use a fluorinated salt of chromium oxide (Cr2O3). In the example given therein, unsupported Cr2O3 is used and turned into a fluorinated salt by co-feeding a mixture of HF and air over the catalyst bed for 18 hours at 380° C. The catalytic gas phase fluorination according to the example given in this document was conducted with the following parameters: the molar ratio of HF: 140 was 7.8:1, the reaction temperature was 220° C., the pressure was 150 psi (˜10 bar), and the contact time was 34 seconds, leading to a 100% conversion of 140 with a selectivity of 70.2% for 142.
EP 1 008 574 A1 describes a catalytic gas phase fluorination of 1,2-dichloroethene (1130) for preparing 142 in the presence of a catalyst. The catalyst is preferably a supported or unsupported fluorinated salt of antimony (in particular SbCl5). In the example 1—similar to EP 1 008 575 A1—unsupported Cr2O3 was turned into a fluorinated salt by co-feeding a mixture of HF and air over the catalyst bed for 18 hours at 380° C. The catalytic gas phase fluorination according to the example 1 was then conducted with the following parameters: the molar ratio of HF:1130 was 6.5:1, the reaction temperature was 220° C., the pressure was 150 psi (˜10 bar), the contact time was 34 seconds, leading to a 88.3% conversion of 1130 with a selectivity of 84.2% for 142.
In the example 2 of EP 1 008 574 A1 a SbCl5 catalyst on active carbon was activated at 50° C. by co-feeding a mixture of HF and nitrogen over the catalyst bed for 18 hours to give the fluorinated salt. The catalytic gas phase fluorination according to the example 2 was then conducted with the following parameters: the molar ratio of HF: 1130 was 6.5:1, the reaction temperature was 120° C., the pressure was 120 psi (˜8 bar), the contact time was 34 seconds leading to a 95% conversion of 1130 with a selectivity of 94.9% for 142.
When looking for an efficient way for the preparation of 1-chloro-2,2-difluoroethane in a large scale the inventors found that the use of the catalysts described in EP 1 008 574 A1 or EP 1 008 575 A1 is not satisfactory. In particular, the published conversion rates and the selectivity towards the preparation of 142 could not be reproduced with the described fluorination system (cf. examples B1 and B2 herein).